Tissue factor- and factor X-dependent activation of protease-activated receptor 2 by factor VIIa
Tissue factor- and factor X-dependent activation of protease-activated receptor 2 by factor VIIa
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DOI：
10.1073/pnas.97.10.5255
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发表时间：
2000-05-09
影响因子：
11.1
通讯作者：
Coughlin, SR
中科院分区：
文献类型：
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作者：
Camerer, E;Huang, W;Coughlin, SR
蛋白水解酶激活受体2(PAR2)由血管内皮细胞和其他细胞表达，其功能和生理激活因子(S)尚不清楚。与PAR1、PAR3和PAR4不同，PAR2不能被凝血酶激活。凝血因子VIIa(FVIIa)和Xa(FXA)是凝血级联中作用于凝血酶上游的蛋白酶，需要辅因子与其底物相互作用。这些蛋白水解酶可引起细胞反应，但其受体(S)尚未确定。我们问FVIIa和FXA是否可以激活PAR，如果是由它们的辅因子呈现的话。FVIIa的细胞辅因子组织因子(TF)与PAR1、PAR2、PAR3或PAR4共表达可使PAR2和PAR1的FVIIa激活依赖于Tf。对FXA的反应也被观察到，但不依赖于外源性辅因子。Tf/FVIIa复合体将失活的酶原因子X(FX)转化为FXA。值得注意的是，当FX存在时，低皮莫尔浓度的FVIIa在表达TF和PAR2的细胞中引起了强烈的信号转导。角质形成细胞和细胞因子处理的内皮细胞的反应表明，PAR2可能由Tf/FVIIa直接激活，并由Tf/FVIIa产生的FXA间接激活，其表达水平为Tf和PAR2。这些结果表明，尽管PAR2不能被凝血酶激活，但它仍可能作为凝血酶的感受器，在损伤和炎症的背景下促进内皮激活。更广泛地说，这些发现强调了辅因子在调节PAR功能和特异性方面的潜在重要性。
Protease-activated receptor 2 (PAR2) is expressed by vascular endothelial cells and other cells in which its function and physiological activator(s) are unknown. Unlike PAR1, PAR3, and PAR4, PAR2 is not activatable by thrombin. Coagulation factors VIIa (FVIIa) and Xa (FXa) are proteases that act upstream of thrombin in the coagulation cascade and require cofactors to interact with their substrates. These proteases elicit cellular responses, but their receptor(s) have not been identified. We asked whether FVIIa and FXa might activate PARs if presented by their cofactors. Coexpression of tissue factor (TF), the cellular cofactor for FVIIa, together with PAR1, PAR2, PAR3, or PAR4 conferred TF-dependent FVIIa activation of PAR2 and, to lesser degree, PAR1. Responses to FXa were also observed but were independent of exogenous cofactor. The TF/FVIIa complex converts the inactive zymogen Factor X (FX) to FXa. Strikingly, when FX was present, low picomolar concentrations of FVIIa caused robust signaling in cells expressing TF and PAR2. Responses in keratinocytes and cytokine-treated endothelial cells suggested that PAR2 may be activated directly by TF/FVIIa and indirectly by TF/FVIIa-generated FXa at naturally occurring expression levels of TF and PAR2. These results suggest that PAR2, although not activatable by thrombin, may nonetheless function as a sensor for coagulation proteases and contribute to endothelial activation in the setting of injury and inflammation. More generally, these findings highlight the potential importance of cofactors in regulating PAR function and specificity.